Devices for transporting a sequence or plurality of articles, also known as conveyors, are well known in the art. Additionally, methods for changing the spacing, or pitch, between consecutive or alternating articles on a conveyor are known. Consequently it has been found that when the spacing between adjacent articles is changed, the speed of the articles in relation to a system can also change. For example, transferring articles from a fast moving conveyor to a slow moving conveyor can generally decrease the article spacing. Conversely, the transfer of articles from a slow moving conveyor to a fast moving conveyor can increase the spacing between adjacent articles. However, these methods can be problematic because a wide variability in the spacing can be introduced and remain after such a transfer, especially at high speed. In processes where an article is affected by subsequent, concurrent, and precisely timed process mechanisms, this variability in article spacing can be unacceptable.
For example, a change in the spacing between a sequence of articles can be introduced with the use of a variable-pitch feed screw. While the use of a variable-pitch feed screw can maintain spacing accuracy better than a direct transfer between conveyors having differing speeds, relative motion between the screw and the article being transferred can cause rapid wear of the screw in a high-speed application or in applications incorporating large article accelerations.
Another method to change the spacing between articles employs the use of two partially parallel endless rail and trolley systems. Here, pivotable and articulated connecting arms interconnect spacing members. The articulated connecting arms pivot at the spacing members and at a point intermediate to adjacent spacing members. The path of a second rail and trolley system is adjusted relative to the first rail and trolley system. This adjustment then determines the amount of spacing experienced by the spacing members. However, this system can be problematic. Forces perpendicular to the rail can be extremely high when the spacing between articles is reduced to near zero, since the articulated connecting arm is nearly perpendicular to the rail. In a process that transports heavy objects over great distances, the resulting forces can become unacceptably high.
Other exemplary systems that provide article orientation utilizing cam paths can be found in Coers, U.S. Pat. No. 6,170,244; and Dunstan, U.S. Pat. No. 4,462,514. Exemplary conveyor systems can be found in Olson et al, U.S. Pat. No. 5,895,332; Noestheden, U.S. Pat. No. 5,220,996; Fortenbery et al., U.S. Pat. No. 6,367,610; Castaldi, U.S. Pat. No. 5,810,540; and Ueno et al., U.S. Pat. No. 5,899,316. Exemplary chains sold by the Tsubakimoto Chain Co., including designations RF-type and BF-type, can be used in conveyor processes that require double-pitched chains or chains having rollers and/or bucket elevators disposed thereon. Other specialty chains suitable for a conveyor are sold by the Daido Corporation of America and include the categories of tortilla chain, citrus chain, mid-pitch hole chain, and D.I.D. pin oven chain.
Therefore, it would be an advantage to provide a conveyor system that is capable of increasing the through-put of a production process system that is capable of maintaining the production speed, as required by the process and yet minimize any forces generated during a spacing operation.